The average number of starts per day over a period
of months or years influences the life of a submersible
pumping system. Excessive cycling affects the life of
control components such as pressure switches, starters,
relays and capacitors. Rapid cycling can also cause
motor spline damage, bearing damage, and motor
overheating. All these conditions can lead to reduced
motor life.
The pump size, tank size and other controls should be
selected to keep the starts per day as low as practical for
longest life. The maximum number of starts per 24-hour
period is shown in Table 3.
Motors should run a minimum of one minute to dissipate
heat build up from starting current. 6-inch and larger motors
should have a minimum of 15 minutes between starts or
starting attempts.
|
|
Table 3 Number
of Starts
| Motor
Rating |
Max.
Starts Per 24 Hr. Period |
| HP |
KW |
Single-Phase |
Three-Phase |
| Up to .75 HP |
Up to .55 |
300 |
300 |
| 1 thru 5.5 |
.75 thru 4 |
100 |
300 |
| 7.5 thru 30 |
5.5 thru 22 |
50 |
100* |
| 40 and over |
30 and over |
- |
100 |
*Keeping starts per day within the recommended numbers
provides the best system life. However, when used with a properly configured Reduced Voltage Starter (RSV) or Variable Frequency Drive (VFD), 7.5 thru 30 Hp three-phase motors can be started up to 200 times per 24 hour period.
|